HENRY J. FRANKLIN. 449 



Distinctive Characters of the Genus. 



Female with mandibles entire or with a single notch, the 

 lower side of their apical margin protruding much more 

 strongly than in Bombus (figs. 46 and 49); labrum triangular 

 in outline(fig. 103); abdomen, over a large part of the dor- 

 sal surface, rather scantily clothed with pile, giving it a shiny 

 appearance ; tip of abdomen usually bent noticeably down- 

 ward and forward ; apical segment of venter with prominent 

 lateral elevations (fig. H); posterior tibiae with outer sur- 

 face convex and well covered with hair (never anything 

 more than a trace of corbicula present) (fig. A); inner side 

 of end of posterior tibia without a row of stout spines (fig. 

 48); posterior metatarsi without a prominent projection at 

 the base on the posterior side (fig. I), and drawn out into 

 a somewhat more prominent projection at the apex, behind 

 the insertion of the second tarsal segment, than in Bombus. 



Male with volsellae and squamae of genitalia membrane- 

 ous, the volsellae long, extending far beyond the tips of the 

 squamse, and without apical projections ; anterior margin 

 of labrum outcurved (fig. 57); hind metatarsi with at least 

 moderately long hind fringes, their outer faces somewhat 

 concaved and usually strongly and rather evenly pubescent ; 

 outer faces of hind tibiae convex and hairy, the fore and hind 

 fringes always of good length. 



This genus, as represented in the New World, is divided 

 into the three following distinct and separate groups : Labo- 

 riosus, Ashtoni and Fernaldce. These groups are all newly 

 established in this paper, and each one bears the name of its 

 typical species. 



Tables of the North American Species of the 

 Genus Psithyrus 



FEMALES. 



1. Occiput black, with little or no light or yellow pile 2. 



Occiput bearing a considerable amount of light or yellow pile... 3. 



2. Pleura bearing light or yellow pile to bases of legs....latitarsiis. 

 Lower portion of pleura covered with dark brown or black pile. 



ashtoni. 



TRANS. AM. ENT. SOC. , XXXVIII. (57) 



